You sure the person you're you read saying Stormlight was a complete trilogy wasn't talking about Mistborn?

And I wouldn't worry about the progression of Stormlight as a series because the fifth book that's currently being written is going to be a finale before a time skip anyway.

In the case of Netflix, I'd say it's different because Netflix has brought that lack of trust on themselves. They even made a small statement about how they didn't want to cancel shows without giving them conclusions then outside of a couple of high profile cases they went on to not change their behaviour at all. (Which was obviously going to be the case, so I don't know why they lied about trying to give shows conclusions).

Authors on the other hand aren't a monolith, George RR Martin isn't responsible for what any other writer promises and visa versa so it's not fair to decide not to read someone else's books because GRRM took a while to write a couple of books.

It's really going to fuck up the format, the whole 3 team group stage thing is awful.